A known method for manufacturing panels or slabs in agglomerate materials, for example constituted by marble and/or sand and/or quartz and/or different small decorative elements (metals, glass, ceramics, wood, precious stones and the like), or granites, quartzes or sands bonded with predetermined quantities of bonding resins comprises various working phases, and more precisely:
a first phase in which the various materials constituting the agglomerate are crushed; PA1 a second phase wherein the crushed materials are mixed in order to obtain a product as homogeneous as possible, during which phase the bonding resins are added; PA1 a third phase of molding and compacting the agglomerate, during which the correct shape is achieved; PA1 a fourth phase of panel hardening, carried out at a predetermined temperature; PA1 a fifth phase in which both faces of the panel are subjected to dressing and polishing; PA1 a sixth phase during which the panel is cut to size, chamfered, gauged and countersunk, and after which the final products are discharged.
Such a method allows panels or slabs in agglomerate materials to be manufactured, which possibly include decorative elements which dignify the appearance of the finished product, said panels or slabs having carefully predetermined lengths, widths and thicknesses; said method is continuously carried out by a special machine.
It has to be stressed that the resins which are used for carrying out such a method play the unique role of bonding the crushed stone particles together; in order to perform this task, several different kinds of bonding resins are used, e. g. polyurethanic, epoxydic, phenolic resins.
However, such a method does not allow the surface coloration or decoration of the slab or panel to be modified at one's choice after its manufacturing.
Document GB-A-1,463,596 discloses a process for colouring a metal or a rigid non-metallic substrate having a surface containing an epoxy resin, said process comprising the following phases: contacting said surface with a temporary carrier bearing one or more vaporisable or sublimable dyestuffs; heating such a combination in order to transfer the dyestuff or dyestuffs from the carrier on the the surface to be coloured; and then removing the temporary carrier.
Besides, document U.S. Pat. No. 4,174,250 discloses an apparatus and a method for imprinting articles, e.g. tiles, by means of the sublimation transfer of dyes into a dye receptive plastic resin surface.
Other methods are known which allow the surface of slabs to be dignified, for example in the case where they would exhibit cracks, fissures or the like.
In this case the exposed surfaces are treated with natural or synthetic resins which penetrate into the cavities; the surface is then carefully polished.
In this case, too, it is not possible to decorate or colour the exposed surface of the material, which is generally shaped as slabs or tiles.
Moreover, according to another method known in the art, the exposed surface of tiles or slabs formed by mixtures of natural materials, such as marble, stone, granite, undergoes a surface polishing treatment, by means of products containing a polyester resin or at least enriched therewith; thereafter, a colouration process of said exposed surface is carried out
GB-A-1444368 relates to a process for the transfer printing of ceramic tiles provided with a coating of a synthetic resin, said synthetic resin having affinity for sublimate disperse dyestuffs.
FR-A-2521489 discloses a process for thermal transfer of sublimate colours on supports which are previously coated with synthetic resins.
U.S. Pat. No. 4,406,662 deals with a process of heat transfer for printing the surface of a filled polymeric article using sublimable disperse dyes.
FR-A-2380901 discloses a process for producing decorated water resistent panels having a polymeric transparent coating, said polymer being advantageously a polyester resin.
U.S. Pat. No. 4,172,418 deals with an electrostatic method and apparatus for carrying out sublimation printing of a substrate wherein a matrix comprising the design to be printed is electrostatically charged in a given polarity and a fine disperse dye powder, oppositely charged, is brought into contact with said matrix.